The present invention relates to a self-propelled snow vehicle and more particularly to a kit for converting a conventional bicycle to such a snow vehicle.
Bicycles or bicycle-type snow vehicles are known. One type is intended merely for down hill travel such as are shown in U. S. Pat. Nos. 4,097,055 and 4,027,891. The ""055 Patent discloses a snow vehicle constructed of a bicycle-like fame supported on in-line front and rear skies wherein the front ski is steered by handlebars. The ""891 Patent discloses a conventional bicycle frame wherein both wheels have been removed and replaced with skies. While this type of snow bicycle are usefull for down hill sledding, particularly in a ski lift accessed slope area, they are of little use for cross-country travel.
Self-propelled snow vehicles also are known. However, attempts to convert a bicycle to a self-propelled snow bicycle by installing a front ski in place of the front wheel have heretofore not been successful. One reason for this lack of success is that simply replacing the front wheel with a ski does not address the problem of poor traction of the vehicle on ice or snow so that propulsion is a problem. Another problem is that a front ski alone does not necessarily provide sufficient flotation to keep the pedals of the bicycle clear of the snow surface.
U. S. Pat. Nos. 3,915,468; 5,482,302; 5,102,153; 5,423,559 and 5,738,361 are illustrative of self-propelled snow vehicles. The vehicles disclosed in these patents have a front ski replacing the bicycle front wheel. It is recognized in these patents that traction on an ice or snow surface is a problem. Accordingly, in each of these patents the rear wheel is modified or replaced so as to accommodate an endless track. The endless track provides improved traction and also improves flotation by distributing the weight of the vehicle over a greater area. Accordingly, the modification to the drive system solves both the traction and flotation problems.
Major drawbacks of these self-propelled snow vehicles are the complication of the drive modifications and the expense of such extensive modifications to the drive system. Such complicated drive systems do not lend themselves to installation by the recreational bicycle owner and are impractical both from the standpoints of complexity, weight added to the bicycle and cost.
Accordingly, it is an object of the present invention to provide a kit that allows for a simple do-it-yourself modification to a conventional bicycle for converting the bicycle to a self-propelled snow bicycle.
Another object of the present invention is to provide a kit for converting a conventional bicycle to a snow bicycle that has improved traction.
A further object of the invention is to provide a self-propelled snow bicycle having improved traction without modification of the conventional chain and rear wheel drive system of the bicycle.
A still further object of the present invention is to provide a self-propelled, pedal powered snow bicycle that is easy to peddle on a snow surface.
Yet another object of the present invention is to provide a kit for converting a bicycle to a self-propelled snow bicycle having improved traction simply by replacing the front bicycle wheel with a ski.
The present invention provides a kit containing a few components for converting a bicycle to a snow bicycle having an enhanced performance in the snow. The kit, when assembled is then attached to the front fork of the bicycle. The attachment replaces the front wheel of the bicycle and includes a ski for both flotation and steering. In addition, the attachment of the kit to the front fork acts to improve the traction of the bicycle rear wheel so the snow bicycle may be self-propelled. Thus, the attachment provides improved traction without the need for extensive modification of the rear wheel such as by adding an endless track or a spiked wheel. In fact, the attachment to the front fork provides better traction for the rear wheel with no modification of the drive mechanism.
In this respect, the kit includes a front fork extension that attaches to the existing front fork of the bicycle and extends below the front wheel dropouts of the fork. At the lower end of the extension is a ski. The ski is journaled adjacent its midpoint to the fork extension lower end. The extension and ski together replace the front wheel of the bike. The length of the extension below the wheel dropouts is greater than the radius of the replaced bicycle wheel. Accordingly, with the extension in place, the entire front end of the bicycle is elevated to a position that is higher than its position when a wheel is attached to the fork.
Elevating the front end of the bicycle accomplishes several things. First, elevating the front end changes the center of gravity so as to locate more weight over the rear tire and reduce weight over the front ski. This rearward shift of weight improves traction and allows greater floatation of the front ski over snow covered ground. Elevating the front end of the bicycle further results in raising the crankshaft of the bicycle and increasing the clearance between the pedals and the ground. With the clearance increased, there is less likelihood of the pedals brushing or plowing into the snow cover as the bicycle settles into soft pack snow or as the bicycle is pedaled through deep snow.
In accordance with the present invention, the kit may be used with a conventional bicycle. Preferably the bicycle is of a type designed for off road travel such as a mountain bicycle or the like. Such a bike usually includes a frame including generally upright head and seat tubes connected by a generally horizontal top tube. A front fork is journaled to the head tube and has a pair of wheel dropouts for receiving the front wheel of the bicycle. The front fork has a pair of brake bosses to mount a center pull or cantilevered front brake mechanism on the bicycle. The upper end of the fork extends through the head tube and is attached to handle bars for steering the front wheel. A pedal driven chain drive provides motive power to a rear wheel.
The wheel dropouts and the brake bosses provide mounting locations for the assembled kit when the front wheel and front brake are removed. The kit of the present invention includes an extension for the front fork. The extension is an elongated member having a transverse rod intermediate its ends that is receivable into the wheel dropouts of the front fork and an upper end that is attachable to the brake bosses. Using both the brake bosses and the wheel dropouts to attach the elongated member to the front fork firmly anchors the member to the front fork and provides stability for the lower end of the member that extends down below the wheel dropouts.
A ski is attached to the lower end of the member. Preferably the ski is similar in construction to a stunt ski in that it has a relatively short and wide footprint (as compared to a downhill ski) and has an upturned leading edge and an upturned trailing edge. The ski is journaled adjacent its midpoint to the lower end of the elongated member so it can pitch up or down with respect to the member. A bias operative between the ski and member tends to maintain the ski in a generally horizontal position.
The length of the member extending below the wheel dropouts is greater than the radius of a wheel normally supported in the dropouts. This causes the front of the bicycle frame to tip upwardly so as to shift the center of gravity rearward and put more of the combined rider and bicycle weight over the rear wheel of the bicycle. More weight on the rear wheel improves traction. It also improves the flotation of the front ski and reduces the likelihood of an accident caused by the ski leading edge plowing into the snow-covered ground. Raising the front of the bicycle also elevates the bicycle pedals to increase the clearance between the pedals and the snow covered ground.
Accordingly, the present invention may be characterized in one aspect thereof by a kit for converting a conventional bicycle to a snow bicycle, the bicycle including generally upright head and seat tubes connected by a top tube, a front steering fork journaled to the head tube, handlebars for turning the steering fork, and the steering fork having and a pair of wheel drop outs for receiving the axle of a bicycle wheel and a pair of bosses for mounting a front wheel brake to the fork, and the kit comprising:
a) an elongated member having a lower end and an upper end;
b) a ski attachable to the elongated member lower end;
c) a bracket adjacent the upper end of the elongated member for removably attaching the member to the brake bosses;
d) a transverse rod intermediate the ends of the elongated member, the rod having opposite ends receivable into the wheel dropouts of the fork wherein the bracket and rod together cooperate to fix an upper portion of the elongated member to the front steering fork thereby extending the length of the steering fork; and
e) the elongated member having a length as measured between the transverse rod and the lower end of the member that is greater than the radius of a bicycle wheel normally supported in the wheel dropouts so as to elevate the head tube of the bicycle to a position that is higher than its position when the fork is supported by a bicycle wheel.